And I'm Audie Cornish. President Obama and Mitt Romney have spent months talking about each other. This week, they finally talk to each other - at least as much as a debate will allow. The first presidential debate is Wednesday night in Denver. The subject is domestic issues, with a focus on the economy. Tomorrow, we'll examine President Obama's past performance as a debater. Today, NPR's Ari Shapiro has this story on Mitt Romney's strengths and weaknesses on the debate stage.

ARI SHAPIRO, BYLINE: Romney's debating skills have improved over many years of political campaigns. In 1994, he ran for Senate against Ted Kennedy in Massachusetts. Most observers believe this debate sealed his defeat.

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SENATOR TED KENNEDY: What will be the impact of that on the budget?

MITT ROMNEY: Well, the impact, I do not know the specific number...

KENNEDY: You don't know the (unintelligible)?

ROMNEY: ...on the impact of that on the budget, Senator Kennedy. I think it's a wonderful idea to take it through piece by piece and...

KENNEDY: That's what you have to do as a legislator. That's exactly what you have to do.

SHAPIRO: Bob Shrum coached Kennedy in that debate. Here's the lesson he took away about Romney.

BOB SHRUM: His greatest weakness is spontaneity because when he's spontaneous, he instinctively seems to say the wrong thing. Like - I'll bet you $10,000.

SHAPIRO: That notorious moment came in Iowa earlier this year with Texas Governor Rick Perry.

SHAPIRO: But in the primaries, those were the exceptions. Overall, Romney dominated his opponents this year. Most pointedly in Florida, where he smacked down Newt Gingrich again and again.

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ROMNEY: My father was born in Mexico. My wife's father was born in Wales. They came to this country. The idea that I'm anti-immigrant is repulsive.

SHAPIRO: Brett O'Donnell coached Romney in that debate. He's trained many top Republican politicians, including John McCain in 2008. He says Romney's style is different from the rest.

BRETT O'DONNELL: He's a little more formal than some of the folks that I've worked with and less aggressive, but I think that style seems to suit him pretty well because it does build the persona of a president.

SHAPIRO: Romney doesn't come across as an orator or a preacher on the debate stage. He's not one to inspire passion or tug at people's heartstrings. Instead, O'Donnell says, he masters the data.

O'DONNELL: I would call him a great technical debater. He has a very solid command of the most important issue in the race, that being the economy, and he's got good command of facts and of policy.

SHAPIRO: Indeed, through the early primary debates, Romney won by appearing to be the adult in the room. On that crowded stage, the other Republican candidates scrambled for points and attention, swiping at each other. Romney held his fire, saving it for the president. Here he is in New Hampshire, two days before that state's primary.

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ROMNEY: I happen to believe that if we want to replace a lifetime politician like Barack Obama, who had no experience leading anything, you have to choose someone who's not been a lifelong politician, who has not spent his entire career in Washington and instead has proven time and again he can lead.

SHAPIRO: Later, Romney had to change tactics. When he was down in the polls, he pulled out those aggressive applause lines that made the audience roar.

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ROMNEY: Have you checked your own investments? You also have investments through mutual funds that also invest in Fannie Mae and Freddie Mac.

NEWT GINGRICH: Right.

SHAPIRO: Romney will need to use both skills on Wednesday. He'll have to appear presidential standing next to the leader of the free world, and he'll also have to debut some dramatic showstoppers to change the dynamic of this race. Karen Hughes coached George W. Bush in presidential debates. She says sharing a stage with the president automatically elevates Romney, and those months of primary debates give him an edge, too.

KAREN HUGHES: It's a skill that you hone on the campaign trail. And so, as you go through a primary season, you engage in lots of debates and you become accustomed to articulating what you believe in short, pithy statements. Not so much when you're the president.

SHAPIRO: For Romney, the stakes on Wednesday could not be higher. It's his best remaining chance to turn the race on its head and take the lead. On his plane last week, Romney told reporters that he expects the American people to listen closely for who can help their family and get the economy going.

ROMNEY: And I expect to be able to describe that in a well - in a way people will understand and if they do, I get elected.

SHAPIRO: In the last few weeks, Romney has spent many days off the campaign trail hunkering down to prepare for these debates instead of rallying supporters. A decisive win on Wednesday would be no accident, but rather the payoff for years of training. Ari Shapiro, NPR News. Transcript provided by NPR, Copyright NPR.